TITLE: GCN CIRCULAR NUMBER: 29107 SUBJECT: GRB 201221C: MASTER optical observtion DATE: 20/12/21 19:41:01 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs V. Lipunov, V.Kornilov, E.Gorbovskoy, N.Tiurina, P.Balanutsa,A.Kuznetsov,K.Zhirkov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, A.Chasovnikov,A.Pozdnyakov, V.Topolev, D.Cheryasov(Lomonosov Moscow State University, SAI, Physics Department), R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA), R. Rebolo, M. Serra(The Instituto de Astrofisica de Canarias), D. Buckley (South African Astronomical Observatory), O.A. Gres, N.M. Budnev (Irkutsk State University, API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov, Yu. Sergienko (Blagoveschensk Educational State University) MASTER-IAC robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Spain (IAC Teide Observatory) was pointed to the GRB201221.78 133 sec after notice time and 208 sec after trigger time at 2020-12-21 18:45:02 UT. On our 11-th (180s exposure) set , obtained 1451 sec after tigger time at 2020-12-21 19:05:45 UT, we haven`t found optical transient within Swift error-box (ra=278.204 dec=34.4108 r=0.05). The 5-sigma upper limit has been about 13.6mag The message may be cited. The galactic latitude b = 18 deg., longitude l = 63 deg. The observations made on zenith distance = 69 deg.The moon (48 % bright part) is 56 deg. above the horizon. The distance between moon and object is 87 Observations started at twilight. The sun altitude is -11.4 deg. The object can be observed till sunrise at 2020-12-22 07:52:15 The 5-sigma upper limit has been about 14.9mag The message may be cited.